What is Down Syndrome?

The human body is a wonderful assembly of a specific amount of cells that are connected together.. Any change in the exact cell count can result in a genetic disorder. Down Syndrome is one such disorder that occurs when there is an issue in the cell division of chromosomes, resulting in an extra chromosome 21. This condition is also referred to as Trisomy 21. “Tri” refers to the presence an extra copy of a chromosome. This syndrome influences not only the physical features of a child, but also the overall intellectual development.

This blog gives complete information about the common questions associated with Down Syndrome, its causes, symptoms, and types. 

What is Down Syndrome in children?

Down Syndrome, which affects around 1 in 800 babies, is a genetic disorder that could impact the body, mind or both. 

A child with Down Syndrome can experience heart defects, difficulty with vision and hearing,  sometimes mental disabilities, heart defects, and other health problems. However, the severity differs from child to child.

What are the causes of Down Syndrome in a child?

Initially when the baby is conceived, the cell division starts with the normal egg cell and normal sperm cell with 46 chromosomes. 

Both the egg and the sperm cells undergo a division by splitting into half, which results in each having 23 chromosomes each. The ideal calculation is, when sperm with 23 chromosomes fertilizes an egg with 23 chromosomes, the baby that’s conceived will have a complete set of 46 chromosomes in it, half inherited from its father and other half from the mother. 

But sometimes during the cell division, there could be an anomaly wherein either a sperm or an egg may retain both copies of chromosome number 21, instead of a single copy. When such a sperm or an egg gets fertilized, then the baby-to-be-born will have 3 copies of chromosome number 21, which is called Trisomy 21 or Down Syndrome

Down Syndrome chromosomes

Who is at risk for Down Syndrome?

There are a number of factors that influence the probability of a child being affected. One important factor is the maternal age. The younger the mother is when she conceives, the greater are her chances of deliver a healthy baby.

However if she conceives after 35 years of age, there are risks of having a baby with chromosomal abnormalities. 

According to research, pregnant women at an advanced maternal age were at a higher risk of delivering a child with Down Syndrome. At 20 years of age, the risk was a mere 1 in 2000, at 35 years it was 1 in 350, 40 years it was 1 in 100, and at over 40 years of age, the risk was higher with 1 in 30 down syndrome cases.

What are the types of Down Syndrome?

Trisomy 21:

Of the three types of Down Syndrome, the most common one is Trisomy 21, which affects 9 percent of cases. In such instances, every cell in the human body will have three copies of chromosome 21 instead of just two as suggested by its name Trisomy. Tri means three, and it is this uneven division that causes this variety of syndrome.

Translocation Down syndrome:

Affecting a total of 4 percent, this is when one of the chromosomes of the 21st pair breaks off its cell division and clings on to the other chromosome, forming an extra material. 

Mosaic Down syndrome:

Being the rarest of all types, which affects only 1 percent of the total children, the Mosaic Down Syndrome occurs when only some cells in the human body have an extra copy of chromosome 21 and not all of the cells. Generally people with this type of chromosomal disorder have milder symptoms than those diagnosed with trisomy 21.

What are the symptoms and signs of Down Syndrome?

The baby with Down syndrome has a unique appearance but the way the genes make the child appear can be remarkably different from one child to the other. 

They have recognizable physical features, health issues, and irregularity in cognitive development. Some of the most common symptoms that children with Down Syndrome have are;

  • Short neck and a small head
  • Flat face with slanting eyes that’s often almond shaped
  • Flat ears and protruding tongue that appears exessively large for the mouth
  • Short, heavily-built body size
  • Flat nasal bridge
  • Unusual flexibility with muscle tone
  • Unusual shaped ears
  • Short fingers and a single transverse palmar crease 
  • Unusually small hands and feet

In terms of learning and behavior, Down Syndrome patients may develop symptoms including;

  • Development delays in speech and language due to hearing impairment
  • Issues related to concentration and attention
  • Difficulty to sleep
  • Slow down in cognitive development
  • Set backs in toilet training
  • Moderate cognitive impairments
  • Tantrums and stubbornness
  • Growth restriction in height
  • Bowleggedness


  • Decreased mental function with a mild IQ level ranging from 50 to 70 to a moderate level of 35 to 50. 
  • mild to moderate gross motor skills
  • Delay in development of fine motor skills

Having said the above, a down syndrome child may be at a higher risk of;

  • Epilepsy
  • Respiratory problems
  • Hearing impairment
  • Alzheimer’s disease
  • Thyroid 
  • Childhood leukemia
  • Hardening of the arteries
  • Cancer
  • Diabetic retinopathy

It is difficult to judge the exact type of Down Syndrome a child might have by simply looking at him/her, as the effects of all the three types have common features and behavior.

Conclusion - What can pregnant women do?

Pregnancy is a boon. And every pregnancy is unique. Therefore women should work along with the fetal medicine experts on the risk factors associated with their specific health status. Trying to become pregnant over 35 years of age might expose you to higher rates of complications including premature birth or low birth weight. But there is nothing to panic about. With appropriate medication while planning for pregnancy, there are better chances for a successful pregnancy.

An NT scan or Nuchal Translucency Scan can be used to assess the development of the fetus during the first trimester of your pregnancy to check for any chromosome related disorders. A 20-week Anomaly screening scan can help assess the baby’s physical development. Your health care provider will brief you about the need for and timing of these scans.

In case upon birth, a child shows any of the signs mentioned above, please contact your health care provider, who may collect a sample of your baby’s blood to analyze and determine the diagnosis.

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